Field of the Invention
Embodiments of the present application relate to the art of a drive unit for differentiating torques of drive shafts connected to right and left drive wheels.
Discussion of the Related Art
PCT international publication WO 2015/008661 describes one example of a torque vectoring device of this kind. The drive gear unit taught by WO 2015/008661 as a torque vectoring device comprises a differential unit for distributing torque delivered from a drive motor to right and left drive wheels, and a differential motor for controlling a torque split ratio to the drive wheels. The differential unit is comprised of a pair of single-pinion planetary gear units. In the differential unit, sun gears are rotated by a torque of the drive motor, ring gears are connected to each other in such a manner as to rotate in opposite directions, and the carriers are connected to drive wheels through driveshafts.
In a vehicle provided with the torque vectoring device taught by WO 2015/008661, the rotary members are arranged parallel to each other so that a power loss may be reduced while allowing the carriers to smoothly rotate relatively to each other. That is, in a vehicle having the torque vectoring device taught by WO 2015/008661, a relative rotation between the right wheel and the left wheel are caused easily by a difference in a friction coefficient and unevenness of the road. However, if the relative rotation between the right and the left wheels is caused too easily, a straight line stability may be worsened. In order to prevent such unintentional relative rotation between the right and the left wheels, a complicated control is required to control a differential motor. In addition, an output torque of the differential motor may be varied to cause vibrations.